1. Field of the Invention
The present invention relates to a watercraft propulsion system and a propulsion machine controlling method.
2. Description of the Related Art
In the conventional art, a watercraft includes a plurality of propulsion machines, a normal watercraft operating unit, and a joy stick watercraft operating unit. The normal watercraft operating unit includes throttle levers, which adjust the outputs of the plurality of propulsion machines; and a steering wheel, which adjusts the rudder turning angle of the plurality of propulsion machines. The joy stick watercraft operating unit includes a joy stick, which causes the hull to move in at least each of the front, rear, left, and right directions. A watercraft operator can operate the watercraft in any of the following control modes: a normal mode, which corresponds to the operation of the normal watercraft operating unit, and a joy stick mode, which corresponds to the operation of the joy stick watercraft operating unit.
Japanese Laid-Open Patent Application No. 2010-132127 discloses a technique that limits the transition from the normal mode to the joy stick mode in the case where the velocity of the hull (hereinbelow, referred to as the watercraft velocity) is a prescribed velocity or greater. According to this technique, it is possible to reduce a large load, which is produced by the water current, that is applied to the propulsion machines, which turn with the transition to the joy stick mode.
Nevertheless, in the technique disclosed in Japanese Laid-Open Patent Application No. 2010-132127, it is necessary to provide the hull with a watercraft velocity detecting device (e.g., a velocity sensor, a GPS receiver, and the like); consequently, if the watercraft velocity detecting device is not provided, then the technique cannot be used, which causes a problem.